Electronic devices, such as integrated circuit dice, are packaged using a variety of materials. For example, plastics, ceramics, and glasses are used as substrates and die carriers, while adhesives and polymers are used to attach dice to substrates or other die carriers. Patent Application Publication No. US 2002/0025602A1 describes a microelectronic assembly with a pre-disposed fill material and associated method of manufacture and is hereby incorporated by reference. This publication describes attaching a microelectronic die to a substrate using solder balls that fix to solder ball pads to form solder joints. Thus, a metal is used to connect the die and substrate. Underfill fills the void between the die and substrate adjacent the solder balls. Underfill improves the structural integrity of a die/substrate assembly. For example, underfill reduces the effects of global thermal expansion mismatch between the die and substrate. That is, underfill reduces the stress and strain on the solder joints. Underfill further protects the chip from moisture, ionic contaminants, and mechanical stresses such as twist, pull, shear, and shock/vibration. Accordingly, the bond between the die and substrate includes at least two materials.
U.S. Pat. Nos. 5,679,977 and 5,852,326 teach that attaching a die to a substrate using a material having a low Young's modulus produces fewer package failures than attaching a die to a substrate using a material having a high Young's modulus, and that improved packaging reliability is obtained by selecting a die attachment material having a very low Young's modulus.
U.S. Pat. No. 6,426,564 describes a system for attaching a plurality of solder balls to an electronic device that includes a heat-resistant tape having a first side comprising a plurality of recesses. The first side of the tape may form an adhesive surface. The recesses are located for registration with a plurality of connection points on the electronic device. The recesses are each adapted to receive and retain a solder ball therein. After placing a solder ball within two or more of the recesses, the first side of the tape may be adhered to the electronic device with the solder balls retained therein. Heating of the solder balls causes them to reflow and adhere to the connection points. After cooling, the tape may be removed, wherein the solder balls remain bonded to the connection points, forming a Ball Grid Array (BGA).